I'm not bitter :) just wanted to say these things had happened because of being in a larger family - some folk are unfussed by it, others not so much! And I was 2 when sibling 1 arrived, so don't recall a time without her around. mum went back to p/t work when I was 12, youngest 7, and it didn't bother us at all, as she worked around dad's work hours, so until my youngest sibling was in 6th year, she was always there to get us on the school bus, meet us coming home, and cook dinner/supervise homework. if anything, I probably 'suffered' (if that's the right word? it wasn't really suffering, but you know what I mean?) more as she really loved going back to work and was far happier when she was working.
re: room sharing - at the time it annoyed me, because we all shared for a few years, then I shared with sibling 2 until I was 15, her 13, then my parents had extended enough that we all got our own rooms - so I had less time in my own room than any of the others IYSWIM? and she was very tidy, whilst I am, um, not, so I was always getting a bollocking for making the room look a mess, which stopped being a problem when we had our own rooms for some reason.
I haven't done badly in life at all, but my siblings, particularly the younger 2, had a very different upbringing from me, and I was expected to be the responsible one all the time, and understand when they got things I could never have had. Regarding the foreign holidays, at the time I was upset/jealous that all friends were going abroad, 2 of my siblings (the middle two) were able to go on foreign school trips that I was unable to do - but I made up for it when I was able to, and am much more widely travelled than siblings 1 and 3 (sibling 2 has ended up living overseas, and has travelled in europe a lot). So overall, it hasn't bothered me - but at the time it did.
we were 7, 5 and 3, when sibling 4 was born, so are 2, 3, and 2 school years apart.
I should add that one sibling has serious chronic health issues, and as such, my parents gave said sibling WAY more attention than the rest of us (they had to really!). said sibling does not get on with the rest of us, to the extent of refusing to attend my wedding, and is not the youngest. My parents have said it was hard having to give so much time and energy to one of us, to the detriment of the other 3. but that would be the same no matter how many children you have I imagine?