we all know the great levels which a baal teshuva has and how loved he is in hashems eyes, but a child born to parents who do not keep taharas hamishpacha has what is known as a pegam which is a kabalistic concept. the many virtues of a baal teshuva may over-ride this disadvantage, and this pegam may be far less than the pegam many ffb’s may have from other things they do, but the pegam which belongs collectively to baley teshuvah is the parents.
let us not forget that avrohom came from terach and see where he got to!
in times gone by when ffb’s were less street wise than today than a “boy” ffb may have contained his pure level of raishis oni which a baal teshuva will almost certainly have lost. [unfortunately today even the ffb’s aren’t what they used to be