It looks like I'll have a large age gap between my kids. my daughter will be 4 years and 4 months old if i get pregnant right now lol and i've been trying 2 years already. so thats unlikely.
I'm also from a family where there was a small age gap, and a large age gap. i have a brother 18 months older than me. we don't talk. i have another brother 8 years younger than me, and a sister 10 years younger than me. the relationship i have with them is very motherly, but to be fair, i left the country when they were 9 and 11 so the relationship didnt really progress further than that.
however! i have a much better relationship with my younger siblings than i do with my older one. thats not to say its the age gap that did it. personally i think its more about your personality, how you are raised and how you're taught to act with your siblings than anything else.
for example. my family was abusive. and by the time i was 6, my older brother was hitting and strangling me. however by the time my younger brother was born, my father was working overseas and visiting twice a year, and my mother had depression, was working and wasnt very involved, so i stepped in to raise my siblings. so i dislike my older brother and am very motherly to my younger ones.
i think in a loving family, age gap means very little
even 10 years. as kids they probably wont be overly close. but by the time your older son is 20, your younger child will be 10 and will know he/she will always have an older brother to protect him/her. then when they're 25 and 35, the younger will have an older sibling to look up to, and get advice from. and at that age, 10 years seems small.