As a previous poster said above, the age difference may mean that their bond/relationship will not be as close as you may like.
By the time your youngest turns 3 and starts being aware of forming strong relationships, your eldest will probably be out with his mates every waking minute, or hiding upstairs in his room watching films or playing on the play-station etc
Atleast you won’t have to worry about them fighting over toys and having to teach them how to share as I doubt a 10 year old will want to play with toys meant for a 3 year old 😂
You shouldn’t really have any sibling “pushing and shoving” to worry about or tantrums and arguing either as your eldest will be long past that stage by the time your youngest comes of age when those behaviours typically begin.
I imagine there are different kinds of challenges that come with harnessing good sibling relationships with bigger age gaps, as opposed to situations where the children are off similar ages (1-3 years age gap etc).
There are 3.5 years between my two children and thankfully they are incredibly close despite that gap, which I would have preferred to have been smaller. The first 12 months were tough in terms of sibling jealousy from my eldest but it was hard for him being in the house all day with me and wanting my attention but me being unable to give it as I was stuck to the baby. When my eldest started school and had his own time and space it definitely made things easier, so you have that benefit too I.e your eldest will be occupied with his normal daily life of being at school with his friends that he probably won’t have need to feel like the new baby is taking you away from him as I think this can be a huge factor in why some sibling relationships don’t start off too well.
I think it helps as my two children are of the same sex as they have identical interests so it’s very easy to cater to them both at the same time.
One of my good friends has two siblings, one who is 2 years older than her, and one who is just under 8 years older than her. Although she didn’t really ‘grow up’ with her eldest sibling because of the age gap, she has the best relationship with him as a result of it. She and her other sibling (the two year age gap) aren’t close at all because they basically squabbled their way through their childhood and jealousies arose for various reasons. She wouldn’t say she is particularly close to her eldest sibling because of the age gap, but she gets on far better with him because that same age gap meant they didn’t have ill feelings towards each other when they were children because they were always at different stages of their childhood and teen years etc.
All this is just my own thoughts and musings though as I can’t really give you any valid advice as I do not have any experience of parenting two children with a larger age gap so I don’t really know what challenges arise from that.
I hope some parents come along who have children with a similar age gap so they can share their experiences with you and give you the guidance you would like.
And huge congratulations on your pregnancy - no matter what future challenges may arise, a new baby in the household will bring you all much happiness I’m sure.