well my 2 ds's actually have the same initials as myself and dh.

ds1 Is Nixon, which was a name we liked and came across and just so happened to be N. Then we found out it had the same name meaning as Nicole it was special.
for his middle name i wanted my dads name cause its a name thats been in his fam for a long time, and my maiden name has not been carried on due to my brother not being able to have kids that so happened to be M and my middle name is M.

so then when ds2 came along i did look more into T names to have the same letter as dh, but it wasnt a MUST. His middle name is James which is dh's middle name and my dads middle name so it all just kinda fell together and fit... he is the only one in the family that will have mail issues. Nixon's mail will be directed Mr N xxxx

now pregnant with our 3rd, we already are in love with a girls name starting with T. and from ds1 & ds2 always if we had a girl her middle name was going to be Joan, which is both my mum and dh's mums name.

so we didnt set out to do this, but it all fell into place that way and we love it, and all have been favourite names not just names we went with because it starts with a specific letter... ofcourse if with bub 3 we loved a name that didnt start with a T or N we would use it over keeping a theme.
but maybe other people have reasonings behind their children's names just like we do, so i dont judge. we find it a very special part of our family to have family names as middle names and that we all have the same initials