Here are a few ideas for you...
Not much is sweeter than a sleeping baby...and that is usually the challenge with newborns, trying to keep them awake. So, instead of fighting it, just take lots of pics of the baby sleeping. These two on Mommy's shoulder are very sweet. You can move the baby around so their face isn't too squished and then start snapping shots. Then just crop the picture in as close as you like it.
These next 4 pictures below belong to my friend in Utah that had these pictures taken of her newborn. She owns the rights to these pictures and is allowing me to use them on my blog.
Be patient with newborns. It's really best to take the pics in the first few weeks since they sleep so much. Just make sure they are fed and that you have time to spare and then lay them on a soft blanket (asleep) and then slowly arrange them how you want them.
My friend gave me a great trick to help keep those little naked babies warm...use a blow dryer to blow warm air around them (not on them) while you are positioning them...the noise will probably help keep them asleep and the warmth will keep them from moving around because they are too cold.
When you want both faces in the picture try and keep the baby as close to the Mom's face as you can.
Here is a sweet one with a Dad and his daughter. Sometimes you can crop out most of the adult and just have the baby as the main subject with a hint of Daddy coming in for a kiss.
Use those siblings! They are usually suddenly interested in being in the picture now that the baby is getting so much attention. Even if they can't hold them up as well as you would like, it still makes for a cute picture. And if they both aren't looking...that's okay too. Candids are fun to have of siblings.
Don't forget to take pictures of those cute little habits the babies have...like putting their fingers or thumbs in their mouths. You will want to remember those things too...it doesn't always stay a habit so get a shot of it while they are doing it.