@sunsetchaos
Because he can't afford to keep it.
And it is far from where he goes to school.
At that, so far they've side stepped just how he will be able to pay for their upkeep.
Living in that small a place himself, the impression is that his finances aren't that great to begin with.
There's been no mention of his being included in his sister's estate.
No mention of whether it was settled on the children...
Which would explain some of the resistance to his taking them in, if the thinking was to divide the children so as to divide the estate amongst those who took in the children.
That's been a problem for millennia, guardians taking advantage of those they were entrusted with.
Certainly there wasn't any concern for the children being shown by the other relatives, yet they were firm on keeping them in-country and within the family.
All of this should be covered in the rest of the series.