do you get your kid's siblings birthday/christmas presents?

my son's dad has an older son and i didnt get him anything for christmas. mind you, i barely had the money to get my own kid stuff for christmas due to the fact that im a single mom. well his dad just called me asking me what i was getting his older son for his birthday and i was just like "i dont know" and he said "oh, you didn't get him anything for christmas and now you aren't getting him anything for his birthday. you're just selfish now".. i never even said i wasn't getting him anything for his birthday. and also my son turns 1 next month and i have to pay for his birthday party and smash cake session. his other son's mom didnt get my son anything for christmas either, so i don't understand why he's being so rude to me.