I assume that you are referring to the section 25a of the German Residence Act which deals with “Granting of residence in the case of well integrated juveniles and young adults”.
In here, section 25a (3) says: “A temporary residence permit pursuant to subsection 2 shall not be granted if the foreigner has been convicted of an offence wilfully committed in the federal territory; fines totalling up to 50 daily rates or up to 90 daily rates in the case of offences which, pursuant to this Act or the Asylum Act, can only be committed by foreigners, shall be ignored as a general principle.”
The reason of expulsion from that type of residence permit, in turn, only refers to the “beneficiaries” or “recipients” mentioned in subsection 2 (“The parents or parent possessing the right of care and custody of a foreign minor who holds a temporary residence permit pursuant to subsection 1”), mostly the concerned parents. In other words, if the parents (or younger siblings) committed an offence exceeding the above stated sentence, they could not get that residence permit.
At the same time, it would also be difficult to get a residence permit according to this law for a young person who committed an offence him/herself, as he or she might get problems to prove his or her good integration (required to be considered for a residency according to §25a).
I hope this refers to your question, however, always feel free to specify or to broach the subject again!
All the best,