I come from a family like this and my husband's family did the same. Coincidentally my husband and I also share the same first letter. Our family gatherings can get confusing so most of us have family nicknames.
And my grandfather Umbridge. My uncles 'Uncle 1', 'Uncle 2' and 'Uncle 3', and my step-aunt, Ugly.
My mum here is 'Unfortunate' (gran and gramp were big Les Miserables fans but couldn't stand French).
Here's my brothers Ulysses and Ussher. And my sister Ungoliant. My youngest sister miscarried, you can find her grave over there, marked with her name: Unobtanium.