Well, the thing is, Jak's Uncle is not actually related to Jak in any way. He is a man without family connections who just happens to have the slightly unfortunate name of Jak's Uncle. This was fine when there was nobody called Jak in Sandover, but Samos, to Jak's Uncle's intense irritation, named the young Mar 'Jak' as a joke.

Despite the lack of an actual connection between the two, Jak's Uncle took to appealing to Jak by actually referring to himself as his uncle when he wanted something, hence "would you be kind enough to loan your dear old uncle ninety Precursor orbs?"

Keira is actually everyone's mother. Don't say anything to her; she's quite selfconscious about it.