Sort relationships by eldest child
Currently, relationships in the Family Members section of Family Tree are sorted by the date of the earliest relationship event. If it's a single parent, there's no relationship, and therefore no event, and thus no date. No date sorts last. This means that illegitimate children -- who are almost always a girl's first -- are always out of order, at the bottom:
Similarly, if a person had multiple spouses, but only the date of the last marriage is known, the earlier marriages are out of order, at the bottom.
My suggestion is to use the birthdate of the eldest child to sort otherwise-undated relationships. So for example, Mária as mother to Zsuzsanna born in 1883 would sort before Mária's marriage to János in 1893.
We already use this as a workaround for correctly sorting multiple marriages, entering an approximate marriage date based on the birth of the eldest-known child for each couple, but this doesn't work for single-parent situations, like the illegitimate birth shown above, and even in the cases where there is a relationship, the workaround forces the entry of a conclusion that is, essentially, a guess. It would be better genealogical practice to use the eldest child as a dating proxy for purposes of sorting family members for display, without making any further claims or conclusions.