If they have different interest, like TV shows, toys, etc. get each of them what they are intersted in and then they can go back and forth with the other toy and learn to share their "own" items with each other. On my sons first bday, he received a toy made by the company "Parents" it was one of those toys where you took a toy hammer and push a ball through the hole to fall down the maze, it is called the Parent Mirror Pound a Ball and they carry it at Target. It also teaches great cooridnation! My son LOVED this toy and played with it everyday for a good 6 months. The balls are different colors and that helped teach him his colrs too! THe same company makes those great stacking toys/cups which are so great with a one year olds development. Since they are sweet baby girls, you can also get the cute "my first baby" doll. This is so cute, it does not have anything that can come off for choking reasons and there is nothing painted on it, the dolls are VERY soft and cuddly and they have a cloth set of bottles, etc. I think you can find all of them at Target!
If they are walking and you have a place to play outside a lot, the push walkers are great, I have tried all of them and the least expensive Fisher Price one with the toys on the front of t is my favorite because it is the sturdiest. THese don't have the ability to go slow though so they have to be stable enough on their feet to not push it too far out in front of them and fall.
Good luck, enjoy their first birthday, it is such a precious time. I know it gets tiring hearing everyone tell you that time goes so fast, but it truly does. My oldest will be 10 this year then I have a 7 almost 8 year old, 4 almost 5 year old and my son just turned 2 in February! I can't believe how right my Mom was when she told me how time flies! Have fun and take every moment in and don't sweat the small stuff! They are only this age once and it is such a GREAT age!!
Blessings to you and your family!!
Happy Birthday little girls!!