Doubts on IUPAC name 1,1'-methylenebis(4-isocyanatobenzene) Wikipedia states  IUPAC name of the above compound as 1,1'-methylenebis(4-isocyanatobenzene) . 

I have a confusion. Shouldn't isocyanate group be given preference over the methylene group? I assume the name as 4,4'-methylenebis(1-isocyanatobenzene) .



Similar is the case with DDT.  Wikipedia states its IUPAC  name as 1,1'-(2,2,2-Trichloroethane-1,1-diyl)bis(4-chlorobenzene) . 

Why is the numbering of carbon with three chlorine atoms done $1$ ? Moreover,  can it be  $1,1'$ in the first place in place of $4,4'$ ? I guess the $\text{diyl}$ term indicates that it is connected to two different carbons(of benzene)  .  

To sum up,  I want to know which chain should I select as parent chain and why .
The isocyanato group is named by prefix (like halogeno-), it's not a principal characteristic group named by suffix. It can be said that these groups have lower priority than the “joint” position.
See the different numberings (examples from the IUPAC nomenclature of organic chemistry, 2013):

P-15.3.2.4.1
(…)

1,1′-oxybis(4-bromobenzene) (PIN)

4,4’-oxybis(2-bromobenzoic acid) (PIN)

Therefore it is named 1,1′-methylenebis(4-isocyanatobenzene), not 4,4′-methylenebis(1-isocyanatobenzene).
(You will probably argue that here, the oxy might have higher priority than bromo group or methylene connector, but “connector priority” is not taken into account.)
See also more rigirous answer to Q: What is the rationale of the IUPAC name for DDT?