 Family trees may be seen as directed acyclic graphs , with a vertex for each family member and an edge for each parent @-@ child relationship . Despite the name , these graphs are not necessarily trees because of the possibility of marriages between relatives ( so a child has a common ancestor on both the mother 's and father 's side ) causing pedigree collapse . The graphs of matrilineal descent ( " mother " relationships between women ) and patrilineal descent ( " father " relationships between men ) are trees within this graph . Because no one can become their own ancestor , family trees are acyclic . 
 Family trees may be seen as directed acyclic graphs , with a vertex for each family member and an edge for each parent @-@ child relationship . Despite <a href='None' title='1'><mark>the</mark></a><a href='negative_concord' title='2'><mark>name</mark></a> , these graphs <a href='negative_concord' title='3'><mark>are</mark></a> <a href='negative_concord' title='4'><mark>not</mark></a>necessarily <a href='negative_concord' title='5'><mark>trees</mark></a> because of <a href='None' title='6'><mark>the</mark></a><a href='negative_concord' title='7'><mark>possibility</mark></a> of marriages between relatives ( so a child <a href='got' title='8'><mark>has</mark></a> a common ancestor on both the mother <a href='null_genetive' title='9'><mark>'s</mark></a>and father <a href='null_genetive' title='10'><mark>'s</mark></a>side ) causing pedigree collapse . The graphs of matrilineal descent ( " mother " relationships between women ) and patrilineal descent ( " father " relationships between men ) <a href='drop_aux' title='11'><mark>are</mark></a>trees within this graph . Because no one can become their own ancestor , family trees <a href='drop_aux' title='12'><mark>are</mark></a>acyclic . 
Family trees may b seen as directed acyclic graphs , wit a vertex for each family member and an edge for each parent @-@ child relationship . Despite no name , these graphs ain't necessarily no trees cus of no possibility of marriages between relatives ( soo a child got a common ancestor on both da mother  and father  side ) causing pedigree collapse . Tdagraphs of matrilineal descent ( " mother " relationships between women ) and patrilineal descent ( " father " relationships between men ) trees within this graph . Bebecuzo one can become their own ancestor , family trees acyclic .