If you look at the whole molecule, you’ll see that the hydrogens in the two CH2 groups are equivalent, i.e. their chemical environments are exactly the same. This means there will be no interactions between them that would lead to splitting, and seeing as the adjacent OH hydrogen does not cause any extra splitting either, the peak will be a singlet.
one peak for the Ch2 groups with integration 4
and one peak for the OH groups with integration 2 ?