14 years between me and youngest sibling.
Today we are very close and I adore her. It was also the best contraceptive possible.
But, a lot depends on how you manage things.
It's not fair to choose to have another child with that age gap and expect the older child to be an unpaid baby sitter, or change what they are used to doing because they now have a new sibling. It's also not fair to expect them to be happy and excited about it if they are not.
I hated being asked to look after the baby when we were out and absolutely mortified at the looks and people tutting about teenage mothers and what a disgrace it was.
It was annoying that just at the stage we could do certain activities as a family we were stuck back at softplay or one parent not being able to participate to look after the baby.
It also didn't help in terms of having my mother available when I was looking at universities or struggling with mental health issues at the time as she was always tired and busy with the baby. I ended up being overly independent and self reliant and moved abroad straight after university for over a decade.