The obligation on the Beis Din to circumcise the son:[2] In the event that one was not circumcised by his father, then it is the obligation of the local Jewish court to circumcise him while he’s still a child [i.e. on the eighth day].

Obligation on child when he becomes an adult: In the event that one was not circumcised by his father, and the local Jewish court did not circumcise him as a child, then he is obligated to circumcise himself upon reaching the age of adulthood.

Mother:[3] The mother of the child is not obligated to circumcise her son even in the event that he was not circumcised by his father, and rather the mitzvah falls upon the local Jewish court.

Other Jews:[4] It is forbidden for one to circumcise a child without the consent of the father. However, in the event that the father did not circumcise his son, and the Jewish court likewise did not circumcise him, then any individual can circumcise the son against the wishes of the father.

[1] Michaber Y.D. 261:1; Admur 432 KU”A 2; See Pesakim Uteshuvos 261:1; See Encyclopedia Talmudit Vol. 46 Erech Mila p. 452-462

[2] Michaber Y.D. 261:1;

[3] Rama Y.D. 261:1; Tur 261; See Pesakim Uteshuvos 261:1; See Encyclopedia Talmudit Vol. 46 Erech Mila p. 449-451

[4] Rama Y.D. 261:1; Tur 261 in name of Rambam; See Pesakim Uteshuvos 261:2; See Encyclopedia Talmudit Vol. 46 Erech Mila p. 448-449