Is it obligatory to maintain ties of kinship with an illegitimate child if the father does not acknowledge him?

There are four causes for the establishment of lineage: the marital bed (al-firash), acknowledgment (al-istilhaq), clear evidence (al-bayyinah), and physiognomy (al-qiyāfah). If the woman was not the father's wife and the father did not acknowledge the child, then his lineage to him is not established. Adultery is not proven merely by an emotional relationship; rather, it is proven by clear evidence (four upright witnesses) or by confession.