Hello. I can provide you with two different options. Number one:
Multum valet coniunctio sanguinis
This phrase literally translates to
'much [things] is worth bond [of] blood' or, somewhat more idiomatic:
'A bond of blood is powerful.'The other option is:
Cognatio multum potest
Literally here, this translates to
'Relationship [has] much influence' in which 'relationship' is closer to the English word 'consanguinity,'
id est 'of the same blood,' thusly applying to relatives.
Personally, I think the first one is more beautiful than the second one. You can google both of them up and you'll find some notable hits that will tell you the same.
Note: you can vary all the U's into V's and I's into J's and vice versa. I simply put it the way I think it'd be nice. I'll give you two examples of using the present day spelling and older spelling:
MVLTVM VALET CONIVNCTIO SANGVINIS
Multum valet conjunctio sanguinis