"Jewish law formally considers the bereaved to be those who have lost any one of the seven close relatives listed in Leviticus (21:1-3): father, mother, wife (or husband), son, daughter, (married or unmarried), brother, and sister (or half-brother and half-sister).
There is no requirement to mourn for adoptive parents, adopted brothers and sisters, or adopted children. But while there is no legal obligation to mourn, there should be "sympathetic mourning," namely abstention from public rejoicing and similar activities' in order to demonstrate a full measure of sorrow."