Double parent after a merge seems to block the pull from another person

Double parent after a merge seems to block the pull from another person

[Olivier Paillat]

Hello

I have a question : 
We are two persons working on the same remote repository
My collegue update the remote repository with his ast changes
Meanwhil I have done a git flow feature that I have finished then I
pulled his last version from the remote repository (git pull origin
develop)
I had a few merge conflicts that I solved
Then I did another flow feature and I finally closed this feature and
push it to origin develop
My collegue then try to get the new remote repository but he told me
that because there were a double parent in my merge commit (but the
very last commit is single parent) he could not get the last version.
I manage git with comitin QtCreator and git bash command when my
collegue use Visual Studio to manage git.

Is it true that a double parent is a problem to get a the last commit
on the remote origin develop ? and in this case how to avoid double
parent ? or is there something else going on ?

Best regards

Olivier Paillat