So love this, Truthisinthewine: your DS1 will not only have 50% of your attention now, he will have a whole extra person to love him and care about him for the rest of his life...that's more love and attention not less. You don't have to split yourself 50/50 between your two sons, you just have an extra person along now when you do stuff, you can still spend just as much time together.
And after 5 of the little blighters, I can say it's so true (apart from % of attention each gets - that's never goin to be exact!)
As for dc1's taking longer to bond with for some mums - I do believe that's often due to all the post-birth injuries - stitches, piles, trying to feed whilst balancing on a rubber ring, after pains, colic, lack of sleep etc etc!! - which are often not so bad next time around.
I know it made my first few weeks as a mum hell but then u get into the swing and bonding takes place and ur so in love.
I found all my children so different it was like meeting a new best friend each time - we loved each other instantly! They cooed and gurgled as much (as soon as they could!) at me (or dh) as we did at them!
I think we're programmed to worry about this, so that we do try to do our best to minimize dc1's stress at having to share us.
Even if they suffer from jealousy (my ds1 did) eldest kids do have certain advantages havin been born first anyway - just read an article last week which said the earlier in the family the child, the brighter he/she would be, just cos the others had less individual time devoted to them!