The couple have two adult children - Kelly 32, and Wayne, 33, and are quick to say they have nine grandchildren - mostly kids they have fostered.
"A lot of our foster children have become our grandchildren over the years ...
"We've just become instant grandparents too."
Sometimes children arrived for a short time in an emergency situation, and some stay for longer than expected, the couple said. Either way, they welcome them with open arms.
"They might come while CYF find a placement or they might come for respite care to give other carers a bit of a break for a few days ... it's a bit of a longstanding joke with CYFs and other carers because our interpretation of short-term and [CYF's idea] is very different."
Their latest child arrived for a few months - "that was five years ago." When she walks through the door from school - you quickly realise she loves them as much as they her.
She hugs them, quickly tells them about her day and how happy she is to be home.
The couple respond as though she is the only one in the room - giving her their undivided attention until she settles. "She's a really good kid."
It's simple to care for them, Mrs Birch said. "For us it was just easy. Natural," she said.
However, it can be a bit difficult when they leave - but this pair know they have done their job. "It can be a bit of a wrench especially when we foster a new-born baby and then they go on for adoption or a Home For Life. What we found was the first one was the hardest because he came to us at 2-hours-old and stayed for six months."
Home For Life is when children who can't be adopted and will never return to family, are placed in a permanent foster home. Mrs Birch said it was difficult when the baby was finally placed.
"It was very hard but it's alright because he is now one of our grandchildren ... When we handed him over his new mum she said 'you can't have too many grandparents'."
They feel privileged to be part of the children's lives, Mr Birch said.
"We feel really blessed with all the babies we have had and to be part of their lives in some way. We've managed to stay in contact in some way. We get lots of emails and photographs and we meet for coffee. We haven't really lost contact with any ... it's all about continuity of care which is important to us."
They have simple advice for those who want to follow their lead. "Just be yourself. Be patient and love them as your own. We have found they respond to consistency and boundaries."
Meanwhile, the couple feel guilty about being acknowledged by Child, Youth and Family. " ...There are so many good foster parents around that do equally or better than us."
