qíng tóu yì hé

情投意合

find each other congenial; to have an affinity with each other

Example:

两人说得情投意合, 只恨相见之晚。
Liǎng rén shuō de qíngtóuyìhé, zhǐ hèn xiāngjiàn zhī wǎn.
They found so much in common that they regretted not having met earlier.

两人谈得情投意合, 相见恨晚。
Liǎng rén tán de qíngtóuyìhé, xiāngjiànhènwǎn.
They both found so much in common they regretted not having met earlier