Use a curve through points to rebuild two of the curves using the end points of the two others and the mid points of the curves you are replacing. (you will have to create a point at the middle of the curve ie on curve>length ratio> .5)
Then use tweak (inside the curve through points command) and finesse it until you are happy.
Use boundary blend pick two curves in each direction and youre in business.
I say this without having any idea what shape you are trying to achieve or which version/ modules of pro you are using.