A father returned to find his wife and two young children hanging from the banister in their Birmingham home, an inquest heard.
Shuhel Miah described the moment he discovered the bodies of the boys, aged one and two, and of his wife Musammat Mumtahana, 22 at their flat in Handsworth.
Mr Miah, 30, told the inquest at Sutton Town Hall he was distraught by the tragedy which happened on October 4, 2006, just a few months after the family had moved into their new home in Radnor Road.
A post-mortem examination revealed Musammat hanged Nahim and Raheem with scarves before hanging herself.
The family were known to social services.
When Mr Miah returned home at 3.30am after a shift as a parcel sorter he found that his wife had locked him out. He eventually gained access to the property 18 hours later after getting help from a neighbour.
A statement read by Coroner Aidan Cotter said: “When I opened the back door there was a bad smell. The curtains were closed and the lights were off. I looked up the stairs and saw the three bodies. I ran out to my father who had come with me and said they are dead and I thought what has she done.”
Mr Miah said his wife had struggled to adjust to life as a housewife in England after they married and she moved from Bangladesh in 2003 and said she had tried to commit suicide on two previous occasions.
He told the inquest: “She thought I was having an affair and came in the bedroom with a kitchen knife and stabbed herself in front of me just below the chest. There was no fight and she must have pre-planned it to get the knife from the kitchen.”
He added: “On January 4, a few months after the stabbing, she ran into the bathroom upset and locked herself in. I managed to get in a few minutes later and stop her from drinking almost a whole bottle of bleach. She was admitted to hospital but never referred for psychiatric tests.”
Detective Sergeant Hordern, of West Midlands Police, told the inquest: “There was no sign of foul play as such and an initial examination showed no other injuries apart from the ligatures.
Det Sgt Hordern said that the circumstances of the deaths were “strange but possible”
Toxicology reports show there was no drink, drugs or other injuries and no signs of a struggle.
Coroner Aidan Cotter said: “It is very strange, you really have to think to make it possible. No one can say what a distraught mother would do.”
The inquest continues.