Kate, 28, and Sharon, 33, met in 2006, civil partnered in 2012 and converted their partnership to marriage in 2015.
But the journey to motherhood wasn't that easy.
"One day, I think after spending time with a baby, we just decided to start researching and get on with it.
"My wife started by looking at our rights as parents to find the best option for us before even looking at things like donors.
"Very quickly, we knew we wouldn't be able to afford anything like IUI or IVF, so our only option was at home AI (Artifical insemination) via a known donor."
The couple had heard about a site called PrideAngel, a worldwide connection site, fertility forum and blog for lesbian, gay, single and infertile couples, wishing to become parents.
The membership website has a bank of more than 5,000 sperm donors willing to donate for free. The site was founded by professional scientists and also offers fertility and insemination products.
But one of the first challenges for the couple was finding a suitable donor. Through PrideAngel, they were put in touch with potential sperm donors, and then began to chat to one they felt would be suitable.
Initially, a lot of their conversations were just via email.
"When we actually agreed to meet the donor, we still had so much to talk about!
"Within email questions, we had already asked the expected questions such as why he wanted to donate, what he was expecting from the procedure, as well as typical health questions.
"Then when we met we chatted more socially about taste in music and films, food, allergies and family history.
"We got to know him as a person, it was nice," added Kate.
But it wasn't as simple as getting on with each other, the couple had to discuss plans about how it would work.
"We had to give him a rough guide as to how often we would need him - it was like business and fun.
"It was a very bizarre experience, and I guess awkward at first - speaking to a complete stranger about fertility cycles, etc. but we had to just keep reminding ourselves of the end result.
"It must have been just as nerve wracking for him as well!"
The mums both knew from the very beginning they never wanted to co-parent with the donor, and this was something they had to communicate straight away.
"For us, the donor's job was purely biological and once we fell pregnant then that's where his journey would end.
"Luckily, he was absolutely fine with that. Sharon and I would be Thomas' only parents.
"He asked whether we could send him a scan picture - although he would have been fine if we had said no, bless him - which we did, but he did not ask for anything else after that.
"He left us alone and never interfered. He was the perfect donor."
As well as this, when the couple were trying to conceive, the law was very vague to their rights.
"We knew if we wanted Sharon to be a named parent then we'd have to be civil partnered at the time of insemination, we also knew that AI (as apposed to natural insemination (NI)) limited the donor's rights as a "parent".
"We had to make a contract displaying what we wanted from the donor (and what he would expect) and make it professional, however with all this in mind it still may not stop the donor applying for access if he were to go to court.
"It was certainly a tough decision to make but we felt we found the perfect donor who was on the same wavelength as us."
Fast forward to today, and the couple aren't oblivious to the fact that their son might one day want to find out who his biological father is.
"There's a constant conversation about it between Sharon and I," says Kate.
"How we approach this we will have to work out when the day comes - it's definitely a tough thing to organise when you don't know how someone will feel about it.
"Thomas may accept where he came from, he may want to know more. Who knows..."
With a three-month-old son, the mums are happily settling in to parenting life.
"We're still battling with sleep, but what parent doesn't? Despite the challenges getting here, family life is truly wonderful and is more than what we ever imagined.
"It's made and still making us stronger as a couple and it gives us a new outlook on life. We love it."
Sharon and Kate blog about their journey into parenthood on LesBeMums.