Royal family tree maker: who inherits the throne?

How the line is worked out

Pick the current ruler and a rule. The panel walks the tree depth first: the ruler's most senior child, then that child's own descendants in the same order, then the next child and their line, and so on. When the ruler's descendants run out it climbs to the ruler's parent and takes the ruler's brothers and sisters and their lines, then the parent's siblings, then further up. The ancestors themselves are the way the crown came and are never listed.

Seniority is birth order as stored in the tree: the order in which you added the brothers and sisters. Dates are free text ("the spring of the long frost"), so the page never guesses an order from them.

Representation: tick Died before the current ruler in a person's sheet and they leave the line, but their children stay where they were. In the example, Crown Prince Tobin fell at the siege of Marrowgate, so under absolute primogeniture his daughter Clemence is heir 1 and his son Benedek heir 2, both ahead of Tobin's younger sister Isaure.

Adopted children count only when you tick the box; fostered children never do. With children of later marriages unticked, a child whose other parent is not that parent's first partner (in the order the sheet lists partners) is left out, with their whole line. A child with an unknown other parent still counts.

Check reads the year number in each person's born and died text and lists every continuity problem: a parent younger than their child, or younger at the birth than the age you set (12 unless you change it; adoptive and foster parents only have to be older); a child born more than a year after a parent died; anyone who is their own ancestor through a loop of parent links; a death before the birth; and, if you turn it on, partners who were never alive at the same time. Tap a problem to centre that person. A date with no number ("the winter the river froze") or with two ("12/3/1802") is listed as not checked, never guessed, and two dates in different eras are not compared, because the check cannot know which era came first. It never changes your tree.

The four rules

• Absolute primogeniture: the eldest child inherits whatever their gender, and each heir's own children come before that heir's younger brothers and sisters.
• Male-preference primogeniture: sons come before daughters, the eldest first within each, and an heir's children still come before that heir's younger siblings. People who count as "other" rank with the daughters.
• Agnatic (male line only): only men descended through an unbroken line of men can inherit; the climb to collateral lines goes through a parent who counts as male.
• Elective or no fixed rule: a council, an assembly or a contest chooses, so the panel says it cannot compute a line.

The two gender-based rules need to know how each person counts, so the edit sheet has an optional Counts for succession as field (male, female or other), blank until you set it. Anyone the line reaches with it blank is listed under Could not place, with everyone who would inherit through them, rather than guessed. The ruler's own gender is never checked, so a reigning queen under an agnatic rule still passes the crown to her sons.

A regnal name ("Aldwen II") is optional; when set, it is the name on the chart and in the line.

What it cannot do

These are four simple rules for fiction, not any real country's law of succession: no exclusions for religion, legitimacy or marriage without consent, and no abdications or regencies. The elective rule is not computed. It finds the line from the people in your tree only, and a person with no succession gender under a gender rule is reported, not placed.

No account and no upload: the tree is saved in this browser, separately from the plain family tree page's, and nothing you type leaves your device. Clearing site data deletes it, so use Save file to keep a copy; the file opens on the plain family tree page too. Export makes a PNG, an SVG or a printable PDF, with the heir numbers on it.