This is how that name should work:
descr_names.txt
Code:
faction: seleucid
characters
Tho
surnames
Gonatas
women
Thoike
descr_names_lookup.txt
text\names.txt
Code:
{Tho} Thõä
{Gonatas} Koinäke
{Thoike} Thäis
world\maps\campaign\BI\descr_strat.txt
Code:
character Tho Gonatas, named character, leader, age 48, , x 158, y 115
character_record Thoike, female, command 0, influence 0, management 0, subterfuge 0, age 29, alive, never_a_leader
relative Tho Gonatas, Thoike, end
(relative character, wife, child, child, child..., end)
If you did everything like that, then when you start the campaign, faction leader named Thõä Koinäke is married to Thäis.
When changing names, I always suggest changing stuff in text\names.txt, as it gives less chance for any mistakes and CTD's to occur.
Most of ingame character names in xgmD don't actually match the names in descr_strat.txt, though I always leave a comment line with the correct reference if I want to change it.
And yes, you can have quite a lot of unused stuff in text\names.txt, only stuff referenced in descr_names_lookup.txt gets looked up by the engine.