Brother's are a pain

Two days ago I got a call from my brother asking if I could pick him up from the airport, not a problem i thought, but kept my mouth shut whilst he told me the time and day, 26th December 20:00 hrs, 8 o' bloody clock boxing day night, I told him that I couldn't as we have the gf's family coming round. Last night the phone rings and its my mum, she makes a bit of smnall talk asking how my son is, if I had finished up at work yet etc etc then she says, you know why I'm really calling don't you, soon as she said that it clicked, she is asking me if I can pick my brother up, I was in the middle of bathing my son, so passed the phone to him to talk to his grandma whilst I thought about it, I then spoke to her a little more and told her i would phone her today and tell her the answer, but i don't know the answer yet.

I spoke to the gf yesterday about it and she said "its not your problem" and I sort of agree, if my brother had chosen an earlier time no probs or a different day. So I am in two minds on what to tell my mum, I checked trains and there are none on boxing day down to kent and I very much doubt there will be any buses/coaches and a taxi will be at least £200 I would have thought.