The so called wider family will have no doubt contributed to the girls's attitude, education and morals that led her to get pregnant by a 13 year old in the first place. To suggest the wider family will lavish this new born child with all the care it needs is pure lunacy.
On this general subject......
Social Services will do everything they can to keep the child with its natural parents....that will include a full assessment of the wider family. That is what they are forced to do, it may not be what they want to do, it may not be what they believe is right but they are forced to do that by the courts unless they can prove the child is in some form of dangerous/neglectful environment.
The social worker invloved will be forced to work with other organisations such as the NHS, occupational health, education etc etc to do everything they can to give the parents all the oppurtunity they need to demonstrate they can act as "adequate" parents.
The social worker may believe from the outset that this is a terrible situation but they will ultimately be subject to cross examination from the parent's (legal aid funded) barrister in court if they try to implement some sort of removal/adoption/fostering strategy. There are some exceptions like emergency removals (potentially only short term) but they will eventually come under the same legal scrutiny anyway.
Sh!t system if you ask me.