“Could partner number 2 be the father?”

I had sex with let's say partner no1 on 19th August 2020. Then partner no2 on 6 September 2020. I took a pregnancy test on the 8th September and it said pregnant. I then took another digital test on 9th September which said 3+ weeks. Meaning it would be the 1st partner. As my kid got bigger his hair started to get red like partner no2 is it even possible for partner no2 to be the father?