The Genes For Love Are Located Within The Major Histocompatibility Complex
Scientifically speaking "Romantic Chemistry / Sexual Chemistry" is determined by the Major Histocompatibility Complex (MHC) a group of proteins that pepper the surface of your cells that help your immune system to recognize and fight pathogens. The MHC genes are also known to influence mate-choice in many vertebrates, and variations in the DNA code of MHC genes are known to influence human partner choice. The sweaty t-shirt experiments demonstrated that MHC influences both body scent and body scent preferences in humans (Wedekind et al., 1995 ,...etc...Kromer et al., 2016), where people with very different MHC genes tend to find each others scent pleasant, while people with similar MHC genes will find each other's scent to smell repulsive. Opposites do attract!
A study in an Asian American population found that MHC-based attraction AKA "Romantic Chemistry" is just as important as "Personality type" when predicting second date offers (Wu et al., 2018). MHC genes also play a role in partner choice of other vertebrates, an facinating study in obligate pair-living lemurs showed that couples with mismatched MHC genes tend to make an extra-pair partner selection the cause of lemur affairs (Schwensow et al., 2008). MHC compatibility is so important that scientists have proposed humans invented kissing as a way to test for chemistry, and this biological phenomenon can even help explain the strength of the female orgasm (Sherlock et al., 2016).
In real life, your sense of smell is your natural radar to detect romantic chemistry in-person, so a good place to meet a romantic life partner is actually your local gym. Alternatively go online and try the "DNA Romance" dating app to unlock information hidden in your DNA and see predictions of sexual chemistry between you and your matched today. DNA Romance is easy to use, simply upload your raw autosomal DNA data file and within ~2 minutes your matches will be ready!