Till Schweiger is unfortunately one of those German directors who seem to "engineer" their movies in order to cater to a maximum degree to a certain target audience. By that I mean that he takes some simple ingredients that he knows will please the audience and loosely connects them to form a film.
He was clearly trying to sell this flick to women, so he took cute children, romance and jealousy, a main character discovering his responsibility in life (an invariant in films by Schweiger), inhibited erotic scenes and some stupid, below-the-belt kind of jokes and glued them together to an incoherent, predictable and largely non-entertaining collage.
Sometimes, the results of Schweiger's industrial film-making approach can be decent, as can be seen with Barfuss. Here however, the plot is just mundane to the point of being non-existing, the jokes are embarrassing and contrary to the first film, even the children are portrayed in such an unrealistic way that they don't convey any of the desired cuteness anymore.
As other reviewers have pointed out before me, the production company probably only wanted to make a quick buck with this, following up on the success of Keinohrhasen. If you think that you like a film formed from the above-mentioned ingredients than you should probably watch Keinohrhasen instead - it's exactly the same, only with a slightly better plot.