No he's not selfish and entitled at all @NorthernDaydreamer and that's a really unpleasant thing to say about an 8 year old boy, who is just worried about having a new brother or sister... I'm sure he's a lovely little boy, and this is just unchartered territory for him.
I cried when my mum said she was having a baby/another child when I was 9 and a half, as I had been an only child up to then, and had all the attention, and the nice ladies across the road (both in their 70s, one widowed and one never married, and both with no children,) made such a fuss of me, and bought me little gifts at random times, like Cadburys Creme Eggs, and packs of smarties, and little pocket money type gifts.... I thought 'the new baby will get all the attention and gifts now!' 
Anyway, the baby came along 6 months after my mum told me she was pregnant, (5 days after my 10th birthday!) and I adored him from the moment I saw him. I have a photo of me with a huge grin on my face, holding my little brother in my arms when he was a day old.
He thought the world of me too, and I'd play with him (hide and seek, and draughts, and Ludo, and Battleship, and card games and so on.) He was proud to introduce me as his sister when he was old enough to do so, and all his mates were like 'oooooh, cool...' as none of them had a sister that much older.
So yeah, tl;dr, if you really want another child, then do try for one, your son will be fine, honestly. 
p.s. The 2 lovely ladies across the road did spoil my brother, but still spoilt me til I was about 16-17, and I was working. Then I used to spoil them! 
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