Hi A.
As I mother of twins myself albeit they were a year old quite some time ago, I can tell you that they do have very different sleep patterns. One of the girls would wake the other. It was a nightmare. My solution was to have the early riser not take a morning nap. By noonish she was ready to sit still while I read stories or we did rhymes etc, so was her sister because she was just waking up. They both went down for the afternoon nap until they were not quite 2. They both went to bed for the night at about 8. Mine were all early risers but it never worked to cut the PM nap, or to wake them so they didn't sleep so long.
Don't ask about turning two because all my kids turned crazy about sleeping then. They all don't need the same amt of sleep. In fact one of mine slept/sleeps 2 hours in 24, one of the twins 4-5 hours in 24, one about 8 hours in 24, and lastly our oldest still sleeps 8-10 hours in 24. Hey they are all adults now but all started this around 2 and continue to this day -- in order of the above sleep patterns they are 32 lawyer with wife and our only grandbaby, 18 one of the twins in college majoring in fine arts, 18 the other twin in college majoring in journalism, and 37 volleyball coach--college level hoping to coach at the international level again.
God bless you and your lovely family
Congrats on the new baby on the way. Hey I met a lady once with 3 children in the grocery cart, twins and then single they were 7 months apart.
K. SAHM married 38 years.