A friend of the South African family, whose three children were found murdered at their home in New Malden, south London, said their mother was struggling to cope with her children’s genetic condition.
The victims, a four-year-old girl and three-year-old twin boys, had Spinal Muscular Atrophy (SMA) which left one in a wheelchair and the others unable to move.
Their mother Tania has been arrested in connection with their deaths.
SMA is a genetic disease that causes muscle weakness and progressive loss of movement.
It’s reported a series of tests revealed the couple carried the disease and that three of their four children might not live into their teens.
The three youngest who were killed required constant care and a friend of the couple said Tania was struggling to cope.
Authorities are continuing to question the 42-year-old graphic designer and said they aren’t looking for anyone else in connection with the incident.
It’s understood their father Gary is now back in the UK from Cape Town with the couple’s eldest child who is not thought to have any health problems.
Post-mortem results are expected later today in London that will reveal how the three children were killed.
Meanwhile, two women, thought to be relatives of the family, are reported to have called for help at a neighbour's house shortly after police arrived at the scene.
The women, one in her 30's and the other in her 50's, went next door and were described as "very, very upset" by the homeowner who let them in.
The cause of deaths has not yet been revealed but post-mortem examination results are expected later today.