Boundary construction at 2 plots on one side

Good evening,

we have a neighbor next to us and one in front of us. The property of the neighbor in front of us borders two properties (neighbor A and us) along one line. How does the permitted maximum extent of boundary construction look in this case? It concerns Rhineland-Palatinate. Here, a maximum of 12 m can be built on one boundary and a maximum of 18 m on all boundaries.

Is the neighbor in front of us now allowed to exceed 12 m on one boundary because two properties border there?

If the neighbor in front of us wants to have more than 12 m of boundary construction on one side, does he only need the approval of the neighbor at the 12 m boundary, or of both, because it is a boundary line?

Thank you very much in advance for your feedback!

Is the neighbor in front of us now allowed to exceed 12 m on a boundary since two properties adjoin there?

No, the length of the boundary structure refers to the one who wants to build or to their property boundary, not to the number of their neighbors or the number of adjoining neighboring properties.