you and your brother is ok. why do you fear? for finger problem, you can have ultrasound scan (3D or 4D). for brain problem, dr. can't tell and you can only know when he goes to school.
your mum's problems are not fatal. if you know it before, you still give birth, right? at least your mum is healthy.
don't worry too much. many healthy children have brain problems and learning problems. they have normal IQ but they have some problems in brain. i'm a teacher so i know more about it.