Can I connect 2 ADSL splitter at 2 wires from 1 phone line ?

yes ofcourse

Logical possible, but practical each phone line can be used for one ADSL connection by mean:

Phone line connects to one splitter to separate data from voice , voice goes to phone for normal use while data used to ADSL connection.

adding the filter which is connected with one input and one output to the voice side only to prevent noise on your phone set.

more explianation:

phone line ----splitter L---------- voice phone----filter-----phone set

                                  L----------  data ------ADSL

In your  case :

Splitter( built in ) L-------phone Line-----Lsplitter                                                   L-------phone Line-----L

One line can provide only one connectivity at same time.

The answer is possible, but there may be problems.

Splitters typically have3 labels: ADSL, Phone and Line. To use a splitter you connect your telephone devices (eg phone, fax or answering machine) to the connection labelled phone, your ADSL modem to the ADSL connection and the line to the wall socket. If you have other telephone wall sockets in the property on the same telephone line you will need to plug in filters between the phone and the wall socket.