Unemployed Shem Davies, aged 29, was overjoyed when 14-year-old Tia gave birth to baby Gracie.
Shem and his former girlfriend Kelly John, 30, became parents to Tia at the age of 15.
Their daughter's boyfriend, Jordan Williams, is 15.
Shem said: 'It is an absolute joy to see Gracie thriving. I'm incredibly proud of Tia. She'll be a brilliant mum. At first I wasn't overly pleased that she was pregnant but I soon got over than. Now it's all about being positive'
A week after Gracie was born Tia celebrated her 15th birthday in the ward surrounded by friends and family.
The teenager, who has been dating Jordan for 18 months and wants to be a hairdresser, said she didn't plan on celebrating her birthday in hospital but added that her baby daughter was the best present she could ask for.
Once mother and daughter have been released from hospital they will be staying with grandmother Kelly so that Tia can finish school.
Grandad Shem, who also has a young son of his own, said he is keen to get stuck in and help Tia and Jordan settle into life.
Jordan, who sat his final GCSE just weeks before Gracie arrived, said he understands responsibility. 'I'm captain of the school rugby team and that's like having 14 kids.'
Source: Daily Mail