brief family history
out of the many offspring the birth parents managed to create - mostly with other partners, there are 4 who have always been told they are full siblings - a one year gap between each
DD1
DD2
DS1
DS2 (although the darling part of DS may not come into it, as they were all put into care pretty much as soon as we were born).
So, DD1 and DD1 look very similar, with DD2 and DS2 looking alike (exact same colouring and facial features).
Out of the 4, birth father's name is on all the birth certificates apart from DD2. But, over the years, SS have always reasurred DD2 that they do in fact share the same father, as she is so similar to DS2. This is important, as only DD1 and DD2 managed to be placed together in care.