in Quebec civil law), if the mother is married to another man, the latter will be defined as the father
Presumed father – Where a presumption of paternity has determined that a man is a childs father regardless of if he actually is or is not the biological father
Social father – where a man takes de facto responsibility for a child, such as caring for one who has been abandoned or orphaned (the child is known as a "child of the family" in English law)
Stepfather – a married non-biological father where the child is from a previous relationship

Fatherhood defined by contact level
Absent father – father who cannot or will not spend time with his child(ren)
Second father – a non-parent whose contact and support is robust enough that near parental bond occurs (often used for older male siblings who significantly aid in raising a child, sometimes for older men who took care of younger friends who have no families)
Stay-at-home dad – the male equivalent of a housewife with child, where his spouse is breadwinner
Weekend/holiday father – where child(ren) only stay(s) with father on weekends, holidays, etc. Non-human fatherhood
For some animals, it is the fathers who take care of the young. Darwins frog (Rhinoderma darwini) fathers carry eggs in the vocal pouch. Most male waterfowl are very protective in raising their offspring, sharing scout duties with the female. Examples are the geese, swans, gulls, loons, and a few species of ducks.
These contain additional material from chromosome 21 and occur in about 2.5% of cases. An isochromosome results when the two long arms of a chromosome separate together rather than the long and short arm separating together during egg or sperm development. Trisomy 21
Trisomy 21 (also known by the karyotype 47,XX,+21 for females and 47,XY,+21 for males) is caused by a failure of the 21st chromosome to separate during egg or sperm development (nondisjunction). As a result, a sperm or egg cell is produced with an extra copy of chromosome 21; this cell thus has 24 chromosomes. When combined with a normal cell from the other parent, the baby has 47 chromosomes, with three copies of chromosome 21. About 88% of cases of trisomy 21 result from nonseparation of the chromosomes in the mother, 8% from nonseparation in the father, and 3% after the egg and sperm have merged. Mosaicism
Mosaicism is diagnosed when there is a mixture of two types of cells: some cells have three copies of chromosome 21 but some cells have the typical two copies of chromosome 21. Mosaicism is the least common form of Down syndrome and accounts for only about 1% of all cases of Down syndrome. Children with mosaic Down syndrome may have the same features as other children with Down syndrome. However, they may have fewer characteristics of the condition due to the presence of some (or many) cells with a typical number of chromosomes.