IP mobility ensures network reachability and session continuity while IPv6 networks are on the move. In the Network Mobility (NEMO) model, the potential for NEMO Mobile Routers (MRs) to interconnect and extend Internet connectivity allows the formation Nested NEMO networks. With MANEMO, nested MRs can be efficiently interconnected in a tree-based structure with Internet access being maintained via a designated Gateway. However, this only supports single-homed Internet connectivity. With the span of wireless access technologies and the popularity of multi-interfaced devices, multihoming support in this scenario becomes critical. A Nested Mobile Network with heterogeneous available Internet access options would allow better overall network performance and optimal utilisation of available resources. In this paper, we present the Multihomed Mobile Network Architecture (MMNA), a comprehensive multihomed mobility solution. It provides a multihoming management mechanism for Gateway Discovery and Selection on top of a multihomed mobility model integrating different mobility and multihoming protocols. It enables a complex nested multihomed topology to be established with multiple gateways supporting heterogeneous Internet access. The results demonstrate that the proposed solution achieves better overall throughput, load sharing, and link failure recovery.