Understanding 絵に描いたように


> **そんな絵に描いたように満ち足りた** ダーズリー家にも、たった一つ秘密があった。  
>  In the Dursley family, _who were the very picture of contentment_ , there
> was just one secret.

My translation of そんな絵に描いたように満ち足りた is purely a guess based on Jisho's
definition of 絵に描いたように as "The very picture of...".

I can't understand how this phrase is used. Literally, I would translate
そんな絵に描いたように満ち足りた as "Contented as though they had painted on such a picture".
So I can kind of see how it works, but what is そんな needed for?

Could you give some other examples using this phrase so I can get a better
feel for how it works?




そんな modifies ダーズリー家, so it means "Such a family, the Dursley family, who were
the very picture of contentment, also had just one secret."




そんな modifies ダーズリー家, so it means "Such a family, the Dursley family, who were
the very picture of contentment, also had just one secret."

