Wesley Williams behaved as if nothing had happened after murdering his ex-partner and her son, a court has heard.
Yvonne Walsh, 25, and her seven-month-old son Harrison were found dead in separate rooms with the curtains drawn at their home in Birmingham in May this year.
Mr Justice MacDuff said Williams' subsequent behaviour, which included posting messages on Ms Walsh's Facebook page and visiting friends, demonstrated how unconcerned he was at what he had done.
The judge told a completely impassive Williams:
You are the only person who knows precisely why you acted as you did, but it is clear that you could not accept being rejected by Yvonne Walsh when you were proposing or intending to propose marriage, and she wanted no further part in a relationship with you.
And you decided to kill her - in fact to execute her.
It was your decision, casually taken, that she had to die.
And then you killed Harrison as well, probably as he lay sleeping in his cot.
More top news
Police are trying to find the driver of the car following the incident in Kingfisher Close, Brownhills.
An unnamed man died at the scene, while a woman was pronounced dead after being taken to St George's Hospital, Tooting, south-west London.
Eastern areas will see a few showers coming in on the northeasterly breeze