The science on parental influence is well documented. This research may be onto something new - an additional layer of influence. But the personality begins to be formed by extrinsic influences within months of being born. Which is to say, it precedes the stage at which you have the ability to make friends.
The relevant research is called "The Strange Situation" by Beebe. The research spanned decades with the same subjects. The universal predictor of adulthood outcomes (relationships, lifestyle, income, drug use, etc) was whether the mother was attentive and capable of attuning to the child.
Incorrect assumption, we do not remain equally plastic / malleable in all domains across the entirety of our life. Attachment style crystallizes around 18 months. Trauma can re-open the issue later in life, but the personality builds in layers, with relationship to primary caretaker (usually mom) being a cornerstone.
The relevant research is called "The Strange Situation" by Beebe. The research spanned decades with the same subjects. The universal predictor of adulthood outcomes (relationships, lifestyle, income, drug use, etc) was whether the mother was attentive and capable of attuning to the child.