This is modelled on the Scandinavian or Dwarvish systems, with extra modifiers to allow for modern relationships styles.
Method : the most direct route from the subject to the relative is traced, and the appropriate term is appended in order. Modifiers are used for previous relationships, depending whether they were ended by death or by the breakup of the relationship. An s may optionally be included to make the word scan better.

People:
Mar Mother
Far Father
Sor Sister
Bror Brother
Dottir Daughter
Sen Son
In Wife / female civil partner
En Husband / male civil partner
Ux Girlfriend / female partner / common law wife
Ex Boyfriend / male partner / common law husband

Modifiers for past relationships:
For Relationship broke up
Ter Partner died

Examples:
Farbror Paternal uncle
Marbrorsdottir Female first cousin by maternal uncle
Farmarsorsensdottir Female second cousin, by paternal grandmother’s sister
Terinsen Stepson, through deceased wife
Uxdottir Stepdaughter, through current common law wife
Marenforin Stepfather’s former wife
Foreninsen Ex husband’s stepson
Marfarmarbrorsensen Cousin Bill (3rd cousin once removed)
Farfarsorsensdottirsen Me to Cousin Bill