A first base station, BS, for handling communication, comprising: a storage device, for storing instructions of: connecting to a communication device; transmitting an addition request to a second BS to request the second BS to allocate at least one radio resource for the communication device, when connecting to the communication device; receiving an addition request acknowledgement comprising a secondary cell group, SCG, configuration configuring a SCG for allocating the at least one radio resource for the communication device, from the second BS; transmitting a radio resource control, RRC, message to the communication device, wherein the RRC message comprises the SCG configuration; receiving a RRC complete message from the communication device, wherein the communication device transmits the RRC complete message in response to the RRC message; performing a determination of a release of the second BS for the communication device; generating a release request in response to the determination, wherein the first BS requests a data forwarding in the release request if the release is caused by at least one measurement result of the SCG, a handover, a SCG failure or a master cell group, MCG, failure, and does not request the data forwarding in the release request if the release is caused by a RRC connection release or a user inactivity; and transmitting the release request to the second BS; and a processing circuit, coupled to the storage device, configured to execute the instructions stored in the storage device. a storage device, for storing instructions of: connecting to a communication device; transmitting an addition request to a second BS to request the second BS to allocate at least one radio resource for the communication device, when connecting to the communication device; receiving an addition request acknowledgement comprising a secondary cell group, SCG, configuration configuring a SCG for allocating the at least one radio resource for the communication device, from the second BS; transmitting a radio resource control, RRC, message to the communication device, wherein the RRC message comprises the SCG configuration; receiving a RRC complete message from the communication device, wherein the communication device transmits the RRC complete message in response to the RRC message; performing a determination of a release of the second BS for the communication device; generating a release request in response to the determination, wherein the first BS requests a data forwarding in the release request if the release is caused by at least one measurement result of the SCG, a handover, a SCG failure or a master cell group, MCG, failure, and does not request the data forwarding in the release request if the release is caused by a RRC connection release or a user inactivity; and transmitting the release request to the second BS; and connecting to a communication device; transmitting an addition request to a second BS to request the second BS to allocate at least one radio resource for the communication device, when connecting to the communication device; receiving an addition request acknowledgement comprising a secondary cell group, SCG, configuration configuring a SCG for allocating the at least one radio resource for the communication device, from the second BS; transmitting a radio resource control, RRC, message to the communication device, wherein the RRC message comprises the SCG configuration; receiving a RRC complete message from the communication device, wherein the communication device transmits the RRC complete message in response to the RRC message; performing a determination of a release of the second BS for the communication device; generating a release request in response to the determination, wherein the first BS requests a data forwarding in the release request if the release is caused by at least one measurement result of the SCG, a handover, a SCG failure or a master cell group, MCG, failure, and does not request the data forwarding in the release request if the release is caused by a RRC connection release or a user inactivity; and transmitting the release request to the second BS; and a processing circuit, coupled to the storage device, configured to execute the instructions stored in the storage device.