Relatives - a surprising omission

Last night I was going through some of these test sentences in a bid to find and plug obvious gaps in Vetela (of which there are still several).  While doing so I realised that, though kinship terms are probably often among the first vocab that many conlangers create, Vetela has for a good eight years got by with just 'mother' (liana) and 'father' (vaana)^[0].  So I set about rectifying that, and this is a summary of what I ended up with:

• There is now a general term for 'sibling' (tona), and brothers/sisters are effectively referred to as male/female siblings (vaitona/koitona)
• Grandparents are 'two-parents', great-grandparents 'three-parents' and so on: kaivaana 'grandfather', suiliana 'great-grandmother'
• Similarly for grandchildren: kailaita grandchild, suilaikoi great-granddaughter (< laikoi 'female child')
• Aunts/uncles are to sisters/brothers as grandparents are to parents, so an aunt is a 'two-sister' (kaikoitona) and a great-uncle is a 'three-brother' (suivaitona)
• The word touzana means direct lineal relation in either direction - i.e. either ancestor or descendent.  These can take the following pre-existing prefixes:
• aku- 'previous': akutouzana 'ancestor'
• kiu- 'subsequent': kiutouzana 'descendent'
• ven- 'immediately previous': ventouzana 'parent'
• in- 'immediately subsequent': intouzana 'offspring' (though the usual way to refer to one's children is still laita 'child')
• Finally, half-siblings are 'parent-siblings', with maternal/paternal half-siblings specified as 'mother-siblings' and 'father-siblings' respectively, e.g. vaakoitona 'paternal half-sister'.

Not yet sure what, if anything, to do about cousins - stuff like kaikoitono laita 'aunt's child' is a bit of a mouthful...

[0] Clearly, coming as I do from a tiny family with little in the way of relations, such things aren't very important to me :)