"The ones in my family that are probably being hurt the worst by this all are the young ones," he said.
"I can't imagine how hard this must be for them to try and understand what's going on."
Announcing the inquiry was now being treated as a potential murder case, Detective Superintendent Paul Fotheringham, of Kent Police, said the disappearance was "totally out of character for Sarah".
He added that she had spoken to her friends about looking forward to the future and "most significantly" has now missed one of her children's birthdays.
At the time of Wellgreen's disappearance she was living under the same roof as her ex-partner, 38-year-old taxi driver Ben Lacomba, and their three young children. She was also in a relationship with recruitment boss Neil James, 45, from Farnham in Surrey.
Lacomba is understood to have been questioned by officers for three days this week, before being released on bail. A keen enthusiast for Nerf guns - a type of toy firearm - he recently set up a club in the village hall, inviting locals to enjoy "two hours of solid fun" and to sign up to his YouTube channel 'Sir Nerfalot'.
But friends said the relationship between Lacomba and Walgreen had grown increasingly "fractious" since she moved back into the family home.
She recently won a series of custody battles against her ex-partner, as well as a bitter court dispute over their mortgage. Days before her disappearance, she had been offered a higher-paid job.
"She called Ben 'The T**t'," said close friend Leanne Edwards, 30, who went for a coffee with the Wellgreen three days before she vanished.
"Sarah didn't want anything to do with him. She just wanted to move on."
It was Neil James, Wellgreen's on-off boyfriend, who raised the alarm on October 10 after she repeatedly failed to respond to his messages.
"On the Tuesday night I spoke to Sarah on the phone at 9.24pm. The conversation went on for about 15 minutes," he said.
"The next morning I tried to speak to her again on WhatsApp and Facebook but there was no reply. I left work early and spoke to her eldest boy, and her mum. Then we called the police."
He added: "She told me it was difficult for her at home. She said she was getting on better with Ben initially, but that it soon deteriorated. It was getting more fractious.
"I've tried to get in contact with Ben since Sarah disappeared but he hasn't responded."
Since his release, Lacomba has returned to picking up his passengers in his taxi. He said he had "nothing at all to say" about his ex-partner's disappearance.
