i will chip in my 2 cents here, if the purpose is to split/disty into 5 ppl, then:-

1. your mum-in-law should just sell the apartment (her kids/your wive can assist her in liquidating the unit while she is still around)
2. then split the money FAIRLY among HER 5 children
3. no one can then argue who got more or who is the favorite etc. Too many times a family end up fighting because of these petty matters, just not worth it.

That only works provided she herself (or anyone for that matter) is currently NOT staying in the said apartment.