When it comes to parents needing care, the division of caregiving duties among siblings is rarely equal, a new study has found.

With people living longer nowadays, the chance that families may have to care for their parents has increased. German and Dutch researchers decided to investigate this further.

They looked at almost 2,500 relevant parent-child relationships in over 640 families. The average age that parents first needed care was 77 and the average age of their children at this point was 49.

The study found that when it came to caregiving, siblings were not equally involved. In fact, in 75% of all cases, only one child became the carer.

Mothers were found to be primarily cared for by their daughters, while sons overall were less willing to become sole carers. In families with no daughters, sons tended to divide the caregiving duties between themselves.

Not surprisingly perhaps, distance was important. Those living close to their parents were twice as likely to become their carers compared to those living far away.

Siblings living in the same household as their parents were almost four times as likely to be their carer.

First-born children were also twice as likely to become carers than their younger siblings. And those who worked or had children of their own were less likely to become their parents' carer.

The study also noted that parents' expectations have a role to play. Where a child had been identified as a possible carer, they were three times more likely to fulfill this role compared to their siblings who had not been identified as a potential carer.

Meanwhile, money also came into it. Children who were mentioned in their parents' will were five times more likely to become carers than children who were not.

The researchers also found that carers often reduce their own working hours or even leave their jobs to look after their parents.

Details of these findings are published in the Journal of Marriage and Family.