I was an only child till the ripe age of 15. When you grow up as an only child, you are lonely. You have no one to play with. You come up with your own games just for one. I never really saw myself as having girls who are 21 months apart. Just one of those happenings. I would rather point out some cons first since everybody always does it the other way around. Con 1: It's hard, I have to take them together everywhere. Two carseats and two small kids in tow is hard when I go to Wal-Mart. Con 2: The fighting between them. Con 3: The jealousy and competition for moms attention. I guess that just about covers my cons. Now to the pros. Pro 1: They have each other to play with and grow up together. I never had that sibling bond. Pro 2: I can raise them at the same time with no gaps in ages. Pro 3: The joy of watching them laugh together. Pro 4: The appreciation I feel for them that only a parent feels. Pro 5: Expanding my heart to allow extra love. My pros will always win!