Amber - its probably a bit early for your sis to have poems / songs etc to help her grieve for her twins, but when she does I found this one really helpful and I printed it and put it beside a copy of my baby's footprints : (Apologies probably a bit twee and not the done thing on MN but all my cynicisim about such things went out the window when I lost my baby )
These are my footprints, so perfect and so small.
These tiny footprints never touched the ground at all.
Not one tiny footprint, for now I have my wings.
These tiny footprints were meant for other things.
You will hear my tiny footprints, in the patter of the rain.
Gentle drops like angels tears, of joy and not from pain.
You will see my tiny footprints in each butterflies' lazy dance.
I'll let you know I'm with you, if you give me just a chance.
You will see my tiny footprints, in the rustle of the leaves.
I will whisper names into the wind, and call each one that grieves.
Most of all these footprints are found in Mummy's heart,
cause even though I'm gone now, we'll never truly part.