Fǎlǜ duì xuèqīn zhījiān de guānxì yǒu tèbié guīdìng.
The law has special rules for relationships between blood relatives.
Tips
usage
血亲 (blood relative) is contrasted with 姻亲 (yīnqīn, in-law / relative by marriage). Both are formal/legal terms; in everyday speech people simply say 亲戚 (qīnqi).