Cathy has a fiance, a Duke of Edinburgh Award and a pension. Cat has a pay-as-you-go phone. The only things they have in common are their names (a smart move if you have got a secret daughter). Both of them have always wanted a sister - just maybe not each other.

Cathy and Cat cannot find their dad’s will and, at their joint birthday party, their mums war over which family their dead dad loved most.

Cathy is forced to take compassionate leave from work but can’t bear to tell Tess, so Cat lets Cathy hide at her house and throws her a party to cheer her up.

Cathy proposes they get Colin a memorial bench but, as Cat doesn’t have the money, she has to improvise. Cathy also agrees to teach Cat how to ride a bike, with disastrous results.

With her mum refusing to go, Cathy’s hen do invitees are Auntie Dawn, Marilyn, Cat and an old school friend. It doesn’t turn out to be the classy, edifying affair Cathy wanted.

It’s the night before the wedding but Cathy can’t enjoy her drink-up as she’s obsessed by a scuff on the wall Marcus made, and the sisters run in to Cat’s old school bully.

Cat decides to take Cathy on their own sister honeymoon to cheer her up. Marilyn finds Colin’s missing will and, together with Tess, they need to tell the girls the shocking news.

Cat and Cathy reel from the news that they have a secret brother - who Cathy just snogged. Marilyn is furious to learn she wasn’t Colin’s only mistress and starts stalking his other lover.

Cat feuds with a rival delivery driver and Cathy loses a fight with a washbasin at work. Tess’s singles holiday is a disaster while Angela becomes Marilyn’s house guest from hell.

Cat & Cathy go to an adult maths GCSE class where the sexy teacher causes ructions. Tess takes a job in the worst place possible, and Angela resorts to kidnap to win back Peter.

Cathy is excited to introduce her siblings to lambing season at Auntie Dawn’s farm, but Tess brings along an unwelcome visitor and Cat brings an unwise gift.

In a bid to heal his rift with Angela, Callum is lured to an eventful Northern Soul Revival. Next day, their Dad Colin still has surprises for his family from beyond the grave.