How to draw a pedigree chart: step-by-step clinical tutorial

Short version. Draw a pedigree by identifying the proband, then working outward through core family structure, partners, and children in birth order. Extend to at least three generations, annotate affected status and reproductive outcomes, add consanguinity where it exists, validate the notation, run any relevant inheritance or risk analyses, and export. Live drawing during consultation beats post-hoc reconstruction for accuracy because the patient can correct you in real time; modern software supports gesture drawing for exactly this purpose.

Step 1 — Identify the proband

The proband is the individual through whom the family was ascertained for clinical evaluation. They are marked on the pedigree with an arrow, usually labelled P. If the individual seeking counselling is distinct from the proband (for example, a sibling of an affected person), they are the consultand and are labelled separately.

Start the pedigree with the proband centred in the appropriate generation. For reproductive-risk consultations, the proband is often the person seeking counselling themselves; for a diagnostic workup, it is the first affected family member to come to attention.

Step 2 — Record the core family structure

Draw the proband's parents above, connected by a horizontal mating line. Draw a vertical line down from the mating line to a horizontal sibship line, and draw each of the proband's siblings along that line in birth order, left to right. Use standard symbols: squares for male sex assigned at birth, circles for female, diamonds for unknown or non-binary. Include the proband's partner (if any) alongside the proband, connected by a horizontal mating line.

Step 3 — Add partners and children in birth order

Extend downward to the proband's children. Draw each child in birth order along a horizontal sibship line. Add partners for children and grandchildren as relevant. Maintain generational alignment: every individual in the same generation sits on the same horizontal row, numbered with Roman numerals (I, II, III) from top to bottom.

Within a generation, individuals are numbered left to right with Arabic numerals, so a specific individual can be referenced by their generation and position (for example, III-2 for the second individual in the third generation).

Step 4 — Annotate affected status, age of onset, and clinical notes

For each affected individual, shade or fill the symbol (fully shaded = affected; half-shaded = carrier; central dot = obligate carrier). Where multiple conditions are tracked on the same pedigree, use quadrant shading with a clear legend.

Record age at assessment (current age or age at death) below each symbol. For affected individuals, record age at onset of the condition if known, and annotate with the diagnosis — use ICD-10 or OMIM codes where available for consistency. Include test results (for example, a BRCA1 variant identified on family sequencing) against the individual who was tested.

Step 5 — Extend to at least three generations

A three-generation pedigree (proband, parents, grandparents) is the clinical minimum for inheritance pattern analysis and for running cancer risk models. See our three-generation family history page for what to record at each level. Include first-degree and second-degree relatives systematically rather than selectively, and ask about maternal and paternal sides equally.

For hereditary cancer risk assessment, extend further where possible, including affected individuals identified in the third or fourth generation. Empirical risk models work best with more information; missing relatives are treated as unknowns rather than as non-carriers.

Step 6 — Add pregnancy outcomes and reproductive history

Reproductive history is clinically important, particularly for recessive-disease counselling and for families with repeated losses. Record:

• Ongoing pregnancies (P inside the symbol), with estimated gestational age.
• Spontaneous abortions (small triangle), with gestational age if known.
• Termination of pregnancy (triangle with diagonal line), with reason if clinically relevant.
• Stillbirths (small filled symbol with SB), with gestational age.
• Assisted reproductive technology (donor gametes, surrogacy) with appropriate conventions.

Step 7 — Annotate deceased individuals and adoptions

Deceased individuals are marked with a diagonal line through the symbol. Record age and cause of death beneath the symbol. For adopted individuals, enclose the symbol in brackets ("[in]" for adopted into the family, "[out]" for adopted out), and distinguish biological from social relationships. Donor-conceived and surrogate-born children have specific conventions; record biological ancestry accurately because it is biology, not social relationship, that drives inheritance.

Step 8 — Add consanguinity

Consanguineous unions are drawn with a double horizontal line between partners. Where the shared ancestry is known, draw it explicitly so Wright's coefficient of relationship and the inbreeding coefficient F can be calculated. If the family is known to have consanguinity further back than is being drawn, annotate this with a note.

Step 9 — Validate the diagram

Before considering the pedigree complete, check:

• Proband arrow is present and points to the correct individual.
• Generational alignment is consistent.
• All relevant first- and second-degree relatives are included.
• Affected status is consistent with recorded diagnosis.
• Ages and dates are plausible.
• A legend accompanies any non-standard notation.
• Pregnancy history is complete rather than only live births.
• Consanguinity is marked where present.

Step 10 — Run analyses and export

Once the pedigree is complete, apply the analyses your service needs: inheritance pattern identification (see our inheritance pattern identifier), Mendelian risk calculations for annotated conditions, cancer risk models (BRCAPRO, MMRpro, PancPRO) where relevant, and consanguinity flagging. Export to PDF for the clinical record, to PNG or SVG for inclusion in reports, and to GEDCOM or JSON for structured data exchange with other systems.

Live consultation vs post-hoc entry

Drawing during the consultation is usually the better approach:

• Real-time correction: the patient can see the pedigree taking shape and correct errors as they arise.
• No memory loss: notes taken from memory after a consultation inevitably lose detail.
• Patient engagement: a visible pedigree is a strong anchor for family discussion.

The practical obstacle is that traditional click-and-drag drawing tools break conversational flow. This is the specific design problem that gesture drawing interfaces solve: keyboard shortcuts and continuous gestures let the clinician build the pedigree without looking away from the patient.

Where live drawing is not possible — a complex multi-branch hereditary cancer pedigree with fifty individuals, say — a hybrid approach works: live sketching of the core family, post-hoc structured entry of extended relatives, and verification at the next appointment.

How Evagene supports this

Evagene is designed for both live-consultation drawing and post-hoc structured entry. The gesture drawing mode uses keyboard shortcuts and continuous gestures so a clinician can draw a pedigree while talking to the patient; symbols are applied automatically based on recorded sex, affected status, and other annotations. The NSGC symbol set is enforced consistently, so the pedigree is visually uniform regardless of who drew it.

Structured entry — via imported GEDCOM 5.5.1, JSON, 23andMe genotype files, XEG, or OCR from an existing pedigree image — is also supported for cases where the pedigree is best built from existing records rather than drawn from scratch. Once built, the pedigree feeds directly into Evagene's Mendelian inheritance calculator, BRCAPRO/MMRpro/PancPRO, consanguinity detection, and AI-assisted interpretation (using your own Anthropic or OpenAI LLM key, encrypted at rest). Export to PDF, PNG, SVG, GEDCOM, and JSON preserves the notation and structured data for the clinical record and for sharing.

The embeddable viewer — available as an iframe, raw SVG, or JavaScript snippet — lets the completed pedigree appear in patient portals, research dashboards, or EHR integration layers without additional tooling.

Frequently asked questions

Related reading

• Pedigree drawing software
• NSGC pedigree notation
• ISCN pedigree symbols
• Three-generation family history
• Gender-inclusive pedigree drawing
• Pedigree chart template
• Clinical genetics pedigree tools